**Question:** Aedes aegypti index near ports should be less than -

A. 0.2
B. 0.5
C. 1.0
D. 2.0

**Core Concept:** Aedes aegypti index (AAI) is a measure of the intensity of transmission of dengue fever in a given area. It is calculated by dividing the number of positive cases by the number of samples tested, multiplied by 100. A lower AAI indicates less dengue transmission risk.

**Why the Correct Answer is Right:** The correct answer is less than **0.2**. An AAI less than 0.2 indicates that fewer than 20% of the individuals tested are positive for dengue fever. This low index suggests a low risk of dengue transmission in the vicinity of ports.

**Why Each Wrong Option is Incorrect:**

A. 0.2: This option is too high, indicating a higher transmission risk than the correct answer.
B. 0.5: This option is also too high, suggesting a higher transmission risk than necessary.
C. 1.0: An AAI of 1.0 indicates that 100% of the tested individuals are positive for dengue fever. This is much higher than the correct answer, suggesting a very high transmission risk.
D. 2.0: Similar to option C, an AAI of 2.0 indicates a high transmission risk, not the low risk indicated by the correct answer.

**Clinical Pearl:** Regular monitoring and controlling the Aedes aegypti index near ports can help public health authorities prevent and control dengue fever outbreaks in the area. Reducing breeding grounds and implementing vector control measures can significantly reduce the AAI and lower the risk of dengue transmission.